1. Field of Invention
This invention pertains to earth boring and more particularly to drill directing apparatus, especially multiple conduit drill pipe employed therewith.
2. Description of Prior Art
It is known to drill a hole in the earth with a rotating bit. In such drilling the bit may be loaded axially either by the weight of the drill stem to which the bit is connected or by application of fluid pressure to a piston or cylinder connected to the drill stem anywhere along its length between the bit and the mouth of the hole. The bit can be rotated by a motor connected to the drill stem anywhere between its inner end adjacent the bit and its other or outer end, which may be out of the hole at the earth's surface. It is known to guide the bit to cause the hole to be bored in any desired direction. Instead of fixing the barrel in the hole and drilling through it, it is also known to provide bit deflection means affixed to the bit or to the drill stem adjacent the bit, such deflection means moving axially in the hole as the bit proceeds.
To take the reaction force of an in-hole bit loading device, an in-hole motor or a bit directing device, it is known to provide anchor means to engage the wall of the hole being drilled. This is shown, for example, in U.S. Pat. No. 556,718, to Semmer which also shows means for advancing an in-hole motor and bit loading device along the hole as it is drilled.
It is also known in the art to orient the pipe from outside the hole as in U.S. Pat. No. 3,561,549 to Garrison et al.
It is also known in the art to transmit electrical data from the hole to the surface, including the use of special pipe to transmit hydraulic fluid and electrical signals. Pat. No. 556,718, issued Mar. 17, 1896, to P. Semmer; U.S. Pat. No. 3,170,137, issued Feb. 16, 1965, to H. Brandt;
It is also known to mount two or three pipes concentrically with supports and including various types of expansion joints.
Applicant also understands that at one time Shell encountered difficulty with floating vessel axial risers and constructed pipe to leave one end of each length of the inner tube free.
It is also known to centralize or prevent skewing by the drill bit in the hole. See. U.S. Pat. No. 3,088,532.